1. Field of the Related Art
The present invention relates to a scanning optical system adjusting device and a scanning optical system adjusting method, and particularly to a technique which enables adjustment of a scanning optical system in the state where a scanning optical system of, for example, an image forming apparatus or the like, is assembled as a unit.
2. Description of the Related Art
A scanning optical system of an image forming apparatus must be adjusted to provide a theoretically correct optical axis position and beam diameter. Therefore, various adjustments must be made including adjustment of the optical axis, attachment error of components and semiconductor laser, optical face tangle error of a rotary polygon mirror, and attachment error of an fθ lens.
In a traditional adjusting method, first, as shown in FIG. 7, a position detection device 102 and a beam diameter measuring unit 103 are provided facing a laser unit 11, at distance positions corresponding to installation positions of photoconductors, not shown, and a light beam cast from the laser unit 11 is split by a beam splitter 104 and made incident on each of them. Then, the position of the optical axis of the light beam is adjusted while it is detected by the position detection device 102, and at the same time, the diameter of the light beam is adjusted while it is measured by the beam diameter measuring unit 103. After that, as shown in FIG. 8, the laser unit 11 is incorporated as a scanning optical system and a scanning optical system assembly unit 1 is thus provided.
However, in the case where the adjustments for the light beam of the semiconductor laser (laser unit 11) are made separately from the incorporation of the scanning optical system assembly unit 1, when the semiconductor laser is incorporated in the scanning optical system, the dimension and attachment accuracy of the components such as a casing 1a, a rotary polygon mirror 12 and an fθ lens 13 shown in FIG. 8 cause inconvenience that the light beam does not exit to a theoretically correct optical axis position that is adjusted before the assembly of the unit or inconvenience that the beam diameter cannot be adjusted to a prescribed value.
In such a case, a work of readjusting the beam position and beam diameter and reassembling the unit is required. The assembly of the unit and the adjustment must be repeated. Therefore, there is a problem that the preparation of the scanning optical system unit requires much time and cost.